Control size of buffer.

diff --git a/helloc.c b/helloc.c
index f43a767..9f983a2 100644 (file)
--- a/helloc.c
+++ b/helloc.c
@@ -31,6 +31,14 @@ static int helloc_open(struct inode *ino, struct file *filp)
                return -ENODEV;
        msg = hello_message[iminor(ino)];
        filp->private_data = msg;
                return -ENODEV;
        msg = hello_message[iminor(ino)];
        filp->private_data = msg;

+       if (filp->f_flags & O_TRUNC) {
+               memset(msg->text, 0, msg->len);
+               msg->len = 0;
+               printk(KERN_INFO "File opened with truncate flags\n");
+       }
+       if (filp->f_flags & O_APPEND) {
+               filp->f_pos = msg->len;
+       }

        return 0;
 }
 
        return 0;
 }
 


@@ -67,18 +75,27 @@ static ssize_t helloc_write(struct file *filp, const char __user *buf,
        int r;
        struct message *msg = filp->private_data;
        /* do not read pass through the size of the message */
        int r;
        struct message *msg = filp->private_data;
        /* do not read pass through the size of the message */

-       if (*pos >= msg->len)
+       if (*pos >= BUFFER_SIZE)

        /* return end of file */
                return 0;
        /* if len is bigger than the rest of the message, clamp it */
        /* return end of file */
                return 0;
        /* if len is bigger than the rest of the message, clamp it */

-       if (len > msg->len - *pos)
-               len = msg->len - *pos;
+       if (len > BUFFER_SIZE - *pos)
+               len = BUFFER_SIZE - *pos;
+

        /* copy message to user space and return error if it fails */
        r = copy_from_user(msg->text + *pos, buf, len);
        /* copy message to user space and return error if it fails */
        r = copy_from_user(msg->text + *pos, buf, len);

-       if (r)
+       if (r) {
+               if (*pos + len > msg->len)
+                       memset(msg->text + msg->len, 0, *pos + len - msg->len);

                return -EFAULT;
                return -EFAULT;

+       }

        /* update the file position */
        *pos += len;
        /* update the file position */
        *pos += len;

+       if (msg->len < *pos) {
+               printk(KERN_DEBUG "Updating size from %d to %lld\n", msg->len, *pos);
+               msg->len = *pos;
+       }
+

        return len;
 }
 
        return len;
 }